Freestyle great Ledecky powers towards Tokyo 2020

Irvine, USA: Six years on from her stunning 800m freestyle victory at the 2012 Olympics, Katie Ledecky is savoring her status as the grand dame, at 21, of distance freestyle.

Ledecky was 15 when she led wire-to-wire in winning the 800m free in London in a race that saw world record holder and British home hope Rebecca Adlington relegated to third.

Four more Olympic golds in Rio two years ago, 14 world titles and 15 world records later, Ledecky heads into the Pan Pacific Championships starting on Thursday in Tokyo knowing she's now the swimmer with a target on her back.

"I guess it's a little different," said Ledecky, but she knows that young rivals such as Australian distance phenom Ariarne Titmus and Canadian Taylor Ruck still have a lot of catching up to do.

"I know that there are a lot of great swimmers out there that are chasing me," Ledecky said. "That motivates me just as much as chasing someone motivated me when I was 15."

Ledecky has made a seamless transition this year from US amateur collegiate swimming to the professional ranks, inking a sponsorship deal with TYR that the manufacturer trumpeted as "the most lucrative partnership in the history of the swim industry."

Ledecky specifically chose to make the move two years before the Tokyo Games, to give herself time to adjust to the new demands on her time.

While some US swimmers struggle with newfound responsibilities, Ledecky has taken it in her stride.